Thanks very much for your reply.
I need to know how much force will be applied in psi to an axle on a 220 lb motorcycle when it hits a bump (or runs into a wall) at 40 mph so I can determine if the axle material I want to use has enough ultimate shear resistance, which in this case is 53,000 psi. Since the motorcycle has suspension, the actual force applied to the axle will be less than what it would be if it had no suspension, therefore, my 40 mph speed is actually on the high side and I'm just using it as a speed that is higher than the axle will see so I know I have a safety margin. If the force on the axle at an impact speed of 40 mph is less than the 53,000 psi shear rating of the material I plan to use, the material will be more than strong enough and my axles won't break when I ride it. The motorcycle is being used for vintage motocross/dirt bike racing.
this is a mechanics of materials problem.
the maximum stess will be in bending (not shear),
where bending stress=Mc/I. (in lbs/in
2 or N/m2 or whatever)
and is about the neutral axis;
if the axle is round, the neutral axis is at its geometric center.
you then calculate the "area moment of inertia"=I,
for circular shape, I=1/4pi
*r
4
c is the distance from the neutral axis (radius of the axle in this case)
M=F x d , and d (distance) would be the radius of the wheel (as if the edge of the wheel was hit from the side, i.e you landed with all the wieght on the outside edge of the wheel, sideways)
the force you caclulate from F=ma, or Fdt=mdv, impulse momentum, so you need the time, or a reasonable estimate. (you know V
2, V
1=0).
you can calculate shear when you have the force and area, Stress (in shear)= F/A
A (area)= the x-sect area of the shaft.
added to bending gives the total, but you will find that shear stress is small in comparison to bending.
you also want to compare your max psi load to the tensile strength of the material, not the ultimate strength.